1. Field
The embodiments discussed herein relate to a core gas removal device and method and, more particularly, to a core gas extraction method in which cleaning pins attached to an ejector plate remove tar and product gas contaminants from cavities of a die.
2. Description of the Related Art
In an internal combustion engine, the cylinder head is positioned above the cylinders and includes a platform containing part of the combustion chamber and the location of the valves and spark plugs. The cylinder head is important to the performance of the internal combustion engine, as the shape of the combustion chamber, inlet passages and ports determines a major portion of the volumetric efficiency and compression ratio of the engine.
A typical cylinder head for an internal combustion engine is formed by casting. A related casting operation is shown in FIG. 1. During a low pressure cylinder head casting process, core gas is generated inside of the upper die 10 and tight plugs are relied on to vent out the die 10. The core gas tends to cool and condense as tar while travelling through the tight plugs 40. Tar adheres itself to the inner walls of the tight plugs 40 resulting in blocked passages.
Because the tight plugs provide locations for core gas venting in a die, if the tight plugs become clogged, the risk of defects related to trapped core gases increase. Therefore, tight plug passages must remain open for venting.
The related processes to clean the tight plugs relied on an operator to manually clean out tar from the tight plugs on every stroke with a rod. However, the amount of reach required for these operators to clean the tight plugs with a rod resulted in safety violations, and was also inefficient due to the amount of time required for an operator to manually clean the tight plugs.
To address the problems with the manual tight plug cleaning process, an automated process was developed in which cleaning pins attached to the ejector plate lowered into the tight plugs during each part ejection cycle. A tar collection box was used as a central location to collect all tar particles extracted by the clean pins from the tight plugs. The tar collection box was located just above the tight plugs such that the clean pins traveled through the tar collection box during each part ejection stroke. However, large tar build-up was observed around the clean pins caused by tar build up in the tar collection box. This occurred because during each cycle, the cleaning pins moved through the excess tar in the tar collection box. As a result, tar build-up was observed on sides of the clean pins at the end of each part ejection/tight plug cleaning cycle. Excess tar accumulation in the tar collection box prevented proper venting of the core gas through the tight plug, resulting in gas related defects such as misruns and “elephant skin” surface defects on the cylinder head.
Therefore, an improved core gas extraction method is desired in order to overcome the above-described problems.